Polyurethane reinforced brush



July 28, 1964 w. A. HARTZ ErAL POLYURETHANE REINFORCED BRUSH Filed Nov. 21, 1962v NVENTORS uralter .Hartz M ichael Kalmar United States Patent O 3,142,031 PGLYURETHANE REINFORCED BRUSH Walter A. Hartz and Michael liallaur, Cuyahoga Falls,

Ukio, assignors to The General Tire it Rubber Company, Akron, lrio, a corporation of Chio Filed Nov. 21, 1962, Ser. No. 239,135 7 Claims. (Cl. 15-179) The present invention relates to improvements in metal brushes, such as are used for polishing and cleaning of metal and other articles, and more particularly to an improved wire brush reinforced with polyurethane and methods of preparing the same.

The improved Wire brush of this invention employs a solid rubbery polyurethane material which surrounds and reinforces the sides of the wire bristles and joins portions spaced from the hub. The polyurethane is preferably made by mixing (a) an organic polyisocyanate, such as tolylene diisocyanate, with a polyol of high molecular weight, such as a dihydroxy terminated polyester, a polyalkylene ether glycol or the like with (b) organic bers or suitable llers. The polyurethane may be cured using excess polyisocyanate or suitable curing agents such as dicumyl peroxide.

Objects of the invention are to provide a simple inexpensive polishing wheel which has improved polishing characteristics, and to increase the durability and useful life of reinforced rotary wire brushes.

Other objects, uses and advantages of the present invention will become apparent to those skilled in the art from the following description and claims and from the drawings in which:

FIGURE 1 is a top plan view on a reduced scale of a mold containing a wire brush embodying the present invention;

FIGURE 2 is a vertical sectional view taken on the line 2 2 of FIGURE 1 and on the same scale;

FIGURE 3 is a fragmentary plan view on a reduced scale of a portion of a brush embodying the present invention; and

FIGURE 4 is a fragmentary vertical sectional view taken on the line 4 4 of FIGURE 3 and on a larger scale.

Referring more particularly to the drawings in Which like parts are identified by the same numerals throughout the several views, FIGURES 3 and 4 show a brush comprising a hub portion 1 having a shaft-receiving opening 2 and a series of locking rings 3 for retaining the wire bristles 4 on the hub. The bristles extend radially outwardly from the hub portion 1, but it will be understood that the arrangement of the bristles and the shape of the polishing wheel may be varied considerably. The spaces S between the bristles 4 are lled with a solid polymerization product, such as a polyester resin composition or a polyurethane composition of the type described herein. Such resin is solidied in situ by molecular growth or by polymerization so as to enclose all but the end portions of the various wire filaments or bristles.

FIGURES l and 2 show a mold 11 which may be used to manufacture wire brushes or polishing wheels according to the present invention. This mold has a cavity adapted to receive conventional Wire brushes and of such size that the bristles bear against the wall of the cavity. As herein shown, the mold has a lower portion 13, a cover 14 and means for fastening the cover 14 to the lower portion of the mold including lugs 15 and nuts 16. A suitable gasket 17 is applied on each side of the surface of the hub to form a seal which prevents liquid from entering into the shaft-receiving opening 2. Means are provided for applying pressure to seal the space berice tween the exterior surface of the hub 1 and the parts of the mold, including spaced collars 18 and bolt 19. The polymerizable composition may be poured through an opening 20 into the mold so as to surround and envelop all of the bristles, a vent 21 being provided to permit escape of air from the mold.

Excellent reinforced wire brushes may be made in accordance with the present invention by embedding the bristle portion of a wire brush in a solid matrix comprising a rubbery copolymer of linear polyesters. These linear polyesters usually comprise (a) a polyhydric alcohol, preferably a dihydric alcohol, such as ethylene glycol, diand tri-ethylene glycols, or the like, and (b) a mixture of at least one saturated dibasic acid and at least one unsaturated dibasic acid as disclosed in copending application Serial No. 836,294, filed August 26, 1959, now Patent No. 3,071,795.

The polyester-encapsulated rotary wire brushes are preferably provided with l to 25 parts of fibrous llers and/ or 1 to 50 parts of mineral llers per 100 parts by weight of polymerizable material. The fibrous fillers include natural fibers such as wool and silk; inorganic iibers, such as asbestos and fiber glass; and synthetic iibers such as nylon, Orion, rayon and Saran. Suitable mineral fillers include calcium carbonate, aluminum silicate (clays), mica, silica and silicon carbide. The amount of fillers is selected so as to give a pourable mix having the properties needed for a polishing wheel. Best results are obtained using a mixture of mineral and iibrous llers including alpha cellulose or finely divided wood cellulose having a particle size of 1 to 100 microns. such as Solka-Floc having a particle size of 35 to 90 microns provides a plastic material having exceptional uniformity and consistency. Good results can be obtained, for example, using a mixture of 1 to 2O parts of clay filler and 5 to 20 parts of Solka-Floc per 100 parts of polymerizable mixture.

According to the present invention improved polishing wheels are made by embedding the wire bristles of a rotary wire brush in a polyurethane composition. Such a composition could be made by mixing (a) about 0.9 to 1.5 equivalent Weights of an organic polyisocyanate with about one equivalent weight of a polyol having a molecular weight of at least 500 (preferably at least 2000), such as a dihydroxy-terminated polyester, a polyalkylene ether glycol or the like, with (b) organic bers or suitable llers, and (if excess isocyanate is not used for curing) (c) suitable curing agents, such as dicumyl peroxide, para or meta-substituted 2,6-dimethylol phenol (see Patent No. 3,028,353) or the like.

The polyurethanes employed in practicing the present invention are prepared by reaction of one equivalent weight of a hydroxy terminated polyester or polyether containing at least 2 terminal hydroxyl groups with about 0.9 to 1.5 equivalent weights of aliphatic or aromatic diisocyanates such as 2,4-toluene diisocyanate, p,p'diisocy anate diphenyl methane, naphthalene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylene diisocyanate, meta phenylene diisocyanate, para phenylene diisocyanate or the like. Such trifunctional isocyanates may also be used in part.

The polyurethane may be cured by excess diisocyanate or by employing various curing agents such as dicumyl peroxide, di-tertiary butyl peroxide and other peroxide curing agents of the general formula R-O-O-R (Where R and R are alkyl, aralkyl or other unsubstituted organic groups) as disclosed, for example in co-pending application Serial No. 694,068, filed November 4, 1957, now Patent No. 2,953,539, or paraor meta-substituted 2,6-di-methylol phenols such as 2,6-dimethylol-3,5-diisopropyl phenol or the like as disclosed, for example, in

A wood cellulose co-pending application Serial No. 748,932, now U.S. Patent No. 3,028,353,

The polyurethane may be made from various polyesters and polyethers (polyols) having a low acid number (i.e., below and preferably below 2) and a molecular weight greater than 500 such as 60/40 poly (ethylene-butylene- 1,4-adipate), 80/ 20 poly (ethylene-propylene adipate), polyethylene adipate or other hydroxy-terminated polyesters disclosed in application Serial No. 694,068 and No. 748,932 or polyallrylene ether glycols, such as polyethylene glycol, polpropylene glycol, mixed polyalxylene ether glycols, such as poly (ethylene-propylene) ether glycol, or other polyethers disclosed in said application Serial No. 748,932. The molecular weight of the polyol (polyester or polyether) is preferably at least 2000 and can be as high as 5000 or even 10,000. Excellent results may be obtained using well-known commercial polyurethane prepolymers. Polyether polyurethane prepolymers are generally prepared by reacting polyols, such as polyethylene glycol or the like with a molecular weight of 1,000 to 4,000 and containing 2 to 4 hydroxyl groups with polyisocyanates having 2 NCO groups. The prepolymer may, for example, be a polyurethane prepared from polypropylene glycol having a molecular weight of about 2000 and 2,4-toluene diisocyanate or a polyurethane prepared from 2,4-toluene diisocyanate and a propylene oxide adduct of glycerol having an average molecular weight of about 2800 to 3100 and capped with a little ethylene oxide during its manufacture to provide 3 primary hydroxyl radicals.

The polyurethanes are preferably prepared by reacting a polyhydric alcohol with a polyisocyanate under anhydrous conditions to form a liquid polymer having essentially (l) all hydroxyl or (2) all isocyanate end groups and then curing by adding equivalent amounts of polyisocyanate or polyhydric alcohol, respectively, as is Well known in the art. When such polyurethanes are used to encapsulate a wire brush according to the method of this invention, a polishing wheel is provided which will function much better than those polishing wheels known prior to this invention.

Example I Fifty parts by weight of a polyester resin made by react ing 1 mol of maleic anhydride, 4 mois of phthalic anhydride, 5 mois of sebacic acid and 10.1 mois of diethylene glycol are intimately mixed with 42.5 parts o styrene, 7.5 parts of acrylonitrile, 2.15 parts of a catalyst (50% benzoyl peroxide in tricresyl phosphate), 10.0 parts of Solka-Floc having a particle size of 35 to 90 microns, 7.5 parts of clay ller, and 1.0 parts of dibutyl tin maleate.

The above materials are then deaerated under vacuum and 35 grams thereof are poured into a mold cavity having a diameter of about 3 inches and a depth of about W16 inches. A Wire brush of the type shown in the drawings having a diameter of about 3 inches is positioned in the mold, a cover plate is attached, and the entire assembly' is then placed in a conventional hydraulic press having its platens heated to 275 F. The press is closed to contact pressure for l0 minutes and is then opened to remove the completed encapsulated wire brush or polishing wheel. The polishing wheel is then cooled to room temperature.

The resulting polishing wheel will operate in excess of l0 hours when operated periodically at 3600 r.p.in. against a stationary test bar with a 1000 gram load whereas a similar wheel made without dialkyl tin maleate or similar material will lose its ilexibility rapidly due to surface hardening and will as a result have a much shorter useful life when subjected to the same conditions.

Example II A reactor which has been flushed with nitrogen is charged with 1 mol of a commercial triol l comprising a 1 The triol used may be Dow 112-3.

propylene oxide adduct of glycerol having an average molecular weight of about 2800 to 3000, such triol being prepared by reacting glycerol with propylene oxide to obtain a polyether which is then reacted with ethylene oxide so that the end groups are primary hydroxyl groups, and a minor amount of benzoyl chloride inhibitor (0.03% by weight based on the weight of the triol). The mixture of the triol and the benzoyl chloride is agitated 30 minutes, and 3 mols of 80/20 toluene diisocyanate (80% of the 2,4 isomer and 20% of the 2,6 isomer) are then added. The reaction mixture is then agitated 2 hours at a ternperature of 25 to 30 C. to insure thorough mixing and is then heated to and maintained at 110 to 115 C. until the viscosity is 1500 to 2000 centipoises at 73 C. More of the 20 toluene diisocyanate is then added to produce an NCO content of about 9.5%. The mixture is then cooled immediately and benzoyl chloride (0.03% by weight based on the total weight of reactants) is added while the temperature is about to 100 C.

One hundred parts by weight of the resulting prepolymer is then mixed with 26 parts of 1,4-butanediol, and the mixture is deaerated under vacuum. The material is then poured into a mold with a wire brush therein as in Example I. The mold is then placed in a hydraulic press having a platen temperature of 320"V F., and pressure and heat are maintained for 90 minutes. The encapsulated wire brush is then removed from the press and heated for 72 hours at 220 F.

The resulting polishing wheel can be operated continuously for more than 10 hours at 3600 r.p.m. with a 1000 gram load against a stationary test bar and will operate much better than conventional encapsulated wire brushes.

Example III A liquid polyester is prepared by heating 1.05 mols of diethyle'ne glycol with l0.2 mois of maleic anhydride and 0.8 mols of adipic acid. The mixture is heated while stirring in a vessel equipped with a reux condenser, said condenser being cooled by lluid maintained at a temperature of about C. and being arranged to permit escape of water vapor but to return higher boiling constituents to the reaction mixture. Heating is continued to maintain boiling conditions until the temperature reaches 225 C. whereupon the reaction mixture is allowed to cool. About 40 parts by weight of the cooled reaction mixture is mixed with 32 parts of styrene, 13 parts of acrylonitrile, l0 parts of Sellia-Floc having a particle size of 35 to 90 microns, 5 parts of clay iiller, 0.l parts of dibutyl tin maleate, and 2.0 parts of a catalyst (50% benzoyl peroxide in tricresyl phosphate).

A wire brush having bristles extending radially from its hub is incorporated in the cavity of the mold 11 so as to rest on the inner mold surface 2S, said mold surface having been previously coated with a layer of any suitable mold lubricant (eg, silicone, carnauba waxes, microcrystalline waxes, etc.). In the mold the hub 1 bears against the gasket 17 and the external edges 26 of the bristles bear against the portion 25a of the inner mold surface 2S. The iluid solidiiable composition mixed as indicated above is poured while in the liquid state through the opening 20 until it rises within the vent 2l, and it is allowed to remain in the mold at 60 C. until it has completely solidified. The completed polishing wheel or brush is then removed from the mold and is mounted on a driven shaft for use in polishing or cleaning metal. It is found that the useful life of such polishing wheel is several times that of similar wheels as described, for example, in United States Patent No. 2,648,084 when operated periodically at a light load such as 1000 grams.

rThe present invention greatly increases the life and cutting ability of encapsulated wire brushes without appreciably affecting the ability of the brush to adapt to complex surfaces.

The polyurethane brush of this invention has remarkable resistance to degradation when operated continuously 3 for long periods of time. For certain purposes, such as the deburring of metal castings, the polyurethane brush is preferred over the polishing wheel of said copending application Serial No. 836,294. For other purposes, such as the deburring of glass, the polishing wheel of the latter application would be preferred.

Unless the context shows otherwise, the term parts means parts by weight and all percentages are by weight throughout the specication and claims.

This application is a continuation-in-part of our copending application Serial No. 836,294, filed August 26, 1959.

It will be understood that the above description is by way of illustration rather than limitation and that in accordance with the patent statutes, variations and modiiications of the specic methods and articles disclosed herein may be made without departing from the spirit of the invention.

Having described our invention, we claim:

1. In a wire brush comprising a fastening portion and a plurality of wire bristles extending therefrom, a solid rubbery material substantially completely surrounding and reinforcing the sides of said wire bristles and joining portions spaced from said fastening portion together, said material being a solid linear polyurethane formed by reacting a linear polyol having terminal hydroxyl groups and a molecular weight of at least 500 with an organic diisocyanate.

2. In a wire brush comprising a fastening portion and a plurality of wire bristles extending therefrom, a solid rubbery material substantially completely surrounding and reinforcing the sides of said Wire bristles and joining portions spaced from said fastening portion together, said material being a solid linear polyester polyurethane formed by reacting a linear hydroxy-terminated polyester with a molecular Weight of at least 500 with an organic polyisocyanate having 2 to 3 functional isocyanate groups, said polyester being the reaction product of a polyhydric alcohol and a polycarboxylic acid.

3. A combination as defined in claim 2 wherein said polyisocyanate is a diisocyanate and said polyurethane is formed by reacting 0.9 to 1.5 mols of said diisocyanate with each mol of said polyester.

4. In a wire brush comprising a fastening portion and a plurality of wire bristles extending therefrom, a solid rubbery material substantially completely surrounding and reinforcing the sides of said wire bristles and joining p0rtions spaced from said fastening portion together, said material being a solid linear polyether polyurethane formed by reacting a linear hydroxy-terminated polyether with a molecular weight of at least 500 with an organic polyisocyanate having 2 to 3 functional isocyanate groups, said polyether consisting of hydrocarbon groups joined by ether oxygen atoms and hydroxyl groups on the ends of the polymer chains.

5. A combination as delined in claim 4 wherein said polyether is a long-chain linear polyalkylene ether glycol and said polyisocyanate is a diisocyanate copolymerizable therewith.

6. A combination as dened in claim 4 wherein said polyurethane is formed by reacting 0.9 to 1.5 mols of said diisocyanate with each mol of said polyether, and said polyether has a molecular weight of about 2000 to 4000.

7. A combination as dened in claim 4 wherein said polyether is a triol formed by reacting propylene oxide with a simple polyol having 3 to 6 carbon atomsy and 3 hydroxyl groups.

References Cited in the iile of this patent UNITED STATES PATENTS 2,431,921 Cook et al. Dec. 2, 1947 2,625,535 Mastin et al. Jan. 13, 1953 2,648,084 Swart Aug. 11, 1953 2,866,774 Price Dec. 30, 1958 3,036,042 Schmidt May 22, 1962 3,071,795 Hartz et al. Jan. 8, 1963 FOREIGN PATENTS 753,227 Great Britain Iuly 18, 1956 

1. IN A WIRE BRUSH COMPRISING A FASTENING PORTION AND A PLURALITY OF WIRE BRISTLES EXTENDING THEREFROM, A SOLID RUBBERY MATERIAL SUBSTANTIALLY COMPLETELY SURROUNDING AND REINFORCING THE SIDES OF SAID WIRE BRISTLES AND JOINING PORTIONS SPACED FROM SAID FASTENING PORTION TOGETHER, SAID MATERIAL BEING A SOLID LINEAR POLYURETHANE FORMED BY REACTING A LINEAR POLYOL HAVING TERMINAL HYDROXYL GROUPS AND A MOLECULAR WEIGHT OF AT LEAST 500 WITH AN ORGANIC DIISOCYANATE. 